Method and apparatus for spiral scan region of interest imaging
First Claim
1. A scanning and data acquisition method for three-dimensional computerized tomographic imaging of a region of interest of an object which is smaller than the object itself and having upper and lower boundaries which are completely within a field of view of an imaging system and radially centered on a predetermined axis, the method comprising the steps of:
- applying cone beam energy from a cone beam source to at least a portion of the object;
defining a source scanning trajectory as a path traversed by the source;
using the cone beam source and an area detector with at least the source movably positioned relative to the object, for scanning about the region of interest of the object;
specifying a source scanning trajectory for completely obtaining Radon data for accurately reconstructing a 3D CT image of the region of interest of the object as comprising only a spiral scan defining a plurality of spaced stages on a predetermined geometric surface surrounding the region of interest, such that each plane passing through the region of interest intersects the scanning trajectory in at least one point, the area detector having a predetermined dimension extending sufficiently along a direction generally parallel to the predetermined axis to span at least two consecutive stages having the largest spacing therebetween;
scanning at a plurality of positions along the source scan trajectory to obtain cone beam projection data corresponding to respective portions of the region of interest; and
processing the cone beam projection data corresponding to energy which passed through the object, to provide a data set which can be reconstructed into an image of the region of interest of the object.
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Abstract
A scanning and data acquisition method and apparatus for three-dimensional computerized tomographic imaging of a region of interest (ROI) of an object which is smaller than the object itself and having upper and lower boundaries which are completely within a field of view of an imaging system comprises merely a continuation of the scan trajectory used for scanning the main portion of the ROI so as to extend past its upper and lower boundaries. In a preferred embodiment, the scan path of the present invention consists of a main spiral scan path comprising a plurality of spiral turns, or stages, for scanning between upper and lower boundaries of the ROI, and at least a portion of an extra single spiral turn of the scan path at each end thereof. For image reconstruction, cone beam data for source positions corresponding to circular portions of the scan are approximated in the present invention by interpolation of data acquired from source positions on the extra spiral turn with data acquired from that turn of the main spiral scan that is adjacent thereto.
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Citations
17 Claims
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1. A scanning and data acquisition method for three-dimensional computerized tomographic imaging of a region of interest of an object which is smaller than the object itself and having upper and lower boundaries which are completely within a field of view of an imaging system and radially centered on a predetermined axis, the method comprising the steps of:
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applying cone beam energy from a cone beam source to at least a portion of the object; defining a source scanning trajectory as a path traversed by the source; using the cone beam source and an area detector with at least the source movably positioned relative to the object, for scanning about the region of interest of the object; specifying a source scanning trajectory for completely obtaining Radon data for accurately reconstructing a 3D CT image of the region of interest of the object as comprising only a spiral scan defining a plurality of spaced stages on a predetermined geometric surface surrounding the region of interest, such that each plane passing through the region of interest intersects the scanning trajectory in at least one point, the area detector having a predetermined dimension extending sufficiently along a direction generally parallel to the predetermined axis to span at least two consecutive stages having the largest spacing therebetween; scanning at a plurality of positions along the source scan trajectory to obtain cone beam projection data corresponding to respective portions of the region of interest; and processing the cone beam projection data corresponding to energy which passed through the object, to provide a data set which can be reconstructed into an image of the region of interest of the object. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A scanning and data acquisition imaging apparatus for three-dimensional computerized tomographic imaging of a region of interest of an object which is smaller than the object itself and having upper and lower boundaries which are completely within a field of view of the imaging apparatus and radially centered on a predetermined axis, the apparatus comprising:
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a cone beam source for applying cone beam energy to at least a portion of the object; an energy detector positioned for receiving cone beam energy that had been applied to said object by said cone beam source; a scanning device for causing relative motion, scanning, between the cone beam source and the object such that the cone beam source moves along a source scanning trajectory relative to the object, while maintaining the energy detector in a position to receive energy that had been applied to said object; trajectory defining means operatively coupled to the scanning device for determining a source scanning trajectory for scanning by said cone beam source about the object, said source scanning trajectory comprising only a spiral scan path for obtaining complete Radon data for accurately reconstructing a 3D CT image of the region of interest of the object, said spiral scan path comprising a plurality of spaced stages on a predetermined geometric surface spanning the region of interest of the object so as to extend past its upper and lower boundaries, such that each plane passing through the region of interest intersects the source scanning trajectory in at least one point, the area detector having a predetermined dimension extending sufficiently along a direction generally parallel to the predetermined axis to span at least two consecutive stages having the largest spacing therebetween; means for acquiring cone beam projection data from said detector at a plurality of source positions along the source scanning trajectory so as to obtain cone beam projection data corresponding to respective portions of the region of interest; and processing means for processing the cone beam projection data corresponding to energy which passed through the object, to provide a data set which can be reconstructed into an image of the region of interest of the object. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification